Solid Fraction Examination at Flow Cessation and Flow Cessation Mechanism of Al-Si-Mg Alloy

2020 ◽  
Vol 14 (5) ◽  
pp. 835-842
Author(s):  
Makoto Nikawa ◽  
Yu Iba ◽  
Minoru Yamashita ◽  
◽  
Keyword(s):  
Solid Fraction ◽  
Eutectic Reaction ◽  
Radiation Thermometer ◽  
Mg Alloy ◽  
Melt Temperature ◽  
Experimental Apparatus ◽  
Accurate Temperature ◽  
Skin Formation ◽  
Primary Crystals ◽  
Immersion Type

The aim of this study is to experimentally determine the solid fraction at the cessation of the flow of a molten Al-Si-Mg alloy (JIS-AC4CH) ceases. In this study, an experimental apparatus to measure the melt temperature during flow was developed and was used to perform highly accurate temperature measurements. An immersion-type optical-fiber radiation thermometer without emissivity correction was used for the temperature measurement device in this apparatus. The solid fraction was calculated from the area of primary crystals when the molten metal at any temperature was quenched. The melt temperature at flow cessation was higher than the eutectic reaction temperature, and the solid fraction in the melt front was approximately 0.2. However, the maximum solid fraction was found at a position slightly away from the melt front toward the pouring gate, and was approximately 0.3. It was inferred for this Al-Si-Mg alloy, that the flow cessation mechanism was a mixture of skin formation and mushy formation types.

Oxide Scale Behavior and its Effect on Oxidation Resistance in Al Alloys Containing Alkaline Earth Metal Elements

2017 ◽  
Vol 380 ◽  
pp. 120-123
Author(s):  
Seong Ho Ha ◽  
Young Ok Yoon ◽  
Nam Seok Kim ◽  
Sung Hwan Lim ◽  
Shae K. Kim
Keyword(s):  
Oxide Scale ◽  
Oxidation Resistance ◽  
Surface Segregation ◽  
Earth Metal ◽  
Mg Alloy ◽  
Initial Oxidation ◽  
Melt Temperature ◽  
Ca Addition ◽  
Constituent Elements ◽  
Scale Behavior

Oxide scale behaviors by surface segregation of Mg, Ca and Be in Al and their effects on oxidation resistance at melt temperature were investigated. With the addition of Ca and Be in Al-7.5mass%Mg alloy, the samples showed a suppressed weight gain. However, in the initial oxidation, Ca added samples exhibited improved oxidation resistance. As a result of oxide layer observation by microscopy, Ca added Al-7.5mass%Mg alloy exhibited the region overlapped by constituent elements, indicating multi-element oxide is formed on the surface. In the oxidation of Al-Mg-Be system, BeO is formed as primary oxide and mixed layer with MgO, while Ca addition in Al-Mg system causes no change in the primary and secondary oxides, but formation of CaMg2Al16O27. BeO and BeAl2O4may contribute to balanced layer by combination between constituent oxides in the Al-Mg-Be system. In the case of Ca addition, CaMg2Al16O27acts as a filler of the cracks in MgO layer.

scholarly journals Modeling an RF Cold Crucible Induction Heated Melter With Subsidence

2004 ◽  
Author(s):  
Grant Hawkes
Keyword(s):  
Vector Potential ◽  
Molten Glass ◽  
Melting Process ◽  
Power Input ◽  
Magnetic Vector Potential ◽  
Cold Crucible ◽  
Magnetic Vector ◽  
Melt Temperature ◽  
Experimental Apparatus ◽  
Energy Equations

A method to reduce radioactive waste volume that includes melting glass in a cold crucible radio frequency induction heated melter has been investigated numerically. The purpose of the study is to correlate the numerical investigation with an experimental apparatus that melts glass in the above mentioned melter. Unique to this model is the subsidence of the glass as it changes from a powder to molten glass and drastically changes density. A model has been created that couples the magnetic vector potential (real and imaginary) to a transient startup of the melting process. This magnetic field is coupled to the mass, momentum, and energy equations that vary with time and position as the melt grows. The coupling occurs with the electrical conductivity of the glass as it rises above the melt temperature of the glass and heat is generated. Natural convection within the molten glass helps determine the shape of the melt as it progresses in time. An electromagnetic force is also implemented that is dependent on the electrical properties and frequency of the coil. This study shows the progression of the melt shape with time along with temperatures, power input, velocities, and magnetic vector potential. Coupled to all of this is a generator that will be used for this lab sized experiment. The coupling with the 60 kW generator occurs with the impedance of the melt as it progresses and changes with time. A power controller has been implemented that controls the primary coil current depending on the power that is induced into the molten glass region.

Heat Transfer Model for an RF Cold Crucible Induction Heated Melter

2003 ◽  
Author(s):  
Grant Hawkes ◽  
John Richardson ◽  
Dirk Gombert ◽  
John Morrison
Keyword(s):  
Vector Potential ◽  
Current Source ◽  
Melting Process ◽  
Transfer Model ◽  
Magnetic Vector Potential ◽  
Cold Crucible ◽  
Magnetic Vector ◽  
Primary Coil ◽  
Melt Temperature ◽  
Experimental Apparatus

A method to reduce radioactive waste volume that includes melting glass in a cold crucible radio frequency induction heated melter has been investigated numerically. The purpose of the study is to correlate the numerical investigation with an experimental apparatus that melts glass in the above mentioned melter. A model has been created that couples the magnetic vector potential (real and imaginary) to a transient startup of the melting process. This magnetic field is coupled to the mass, momentum, and energy equations that vary with time and position as the melt grows. The coupling occurs with the electrical conductivity of the glass as it rises above the melt temperature of the glass and heat is generated. Natural convection within the molten glass helps determine the shape of the melt as it progresses in time. An electromagnetic force is also implemented that is dependent on the electrical properties and frequency of the coil. This study shows the progression of the melt shape with time along with temperatures, power input, velocites, and magnetic vector potential. A power controller is implemented that controls the primary coil current so that the power induced in the melt does not exceed 60 kW. The coupling with the 60 kW generator occurs with the impedance of the melt as it progresses and changes with time. With a current source of 70 Amps (rms) in the primary coil and a frequency of 2.6 MHz, the time to melt the glass takes 0.8 hours for a crucible that is 10 inches in diameter and 10 inches high.

Rheo-Forming AZ91D Magnesium Alloy Using Enthalpy Equilibrium Electromagnetic-Stirring Process

2016 ◽  
Vol 256 ◽  
pp. 263-269
Author(s):  
Xiao Li Zhang ◽  
Tong Min Wang ◽  
Chao Zhang
Keyword(s):  
Solid Particle ◽  
Solid Fraction ◽  
Solid Particles ◽  
Electromagnetic Stirring ◽  
Mg Alloy ◽  
Semisolid State ◽  
Pouring Temperature ◽  
Az91d Magnesium Alloy ◽  
Step Effect ◽  
Metal Processing

An enthalpy equilibrium electromagnetic-stirring process was introduced to semisolid metal processing for rheoforming route. AZ91D was die-casted under normally liquid state of Mg alloy, semisolid state of Mg alloy stirred using traditional EM-stirrer and an enthalpy equilibrium EM-Stirrer, respectively. Further step, effect of pouring temperature on microstructures and tensile properties of castings was researched in the introduced process. Experimental results indicated that samples of rheo-diecasted in the introduced process showed globular primary solid particle microstructure and better comprehensive mechanical properties, typical microstructures consisting of globular primary α-Mg grains and pseudoeutectic organization was observed in the castings with low solid fraction, while in higher solid fraction, the microstructure comprised of agglomerating primary solid particles and Mg17Al12 of divorced eutectic. With decreasing pouring temperature, the density of primary solid particles increased greatly, the size of primary solid particle evolved to coarse.

Manufacturing Slurry and Rheocasting of Hypereutectic Al-Si-Cu-Mg Alloy

2012 ◽  
Vol 706-709 ◽  
pp. 420-425
Author(s):  
Yasuhiro Uetani ◽  
Nanako Mori ◽  
Masayoshi Dohi ◽  
Kenji Matsuda ◽  
Susumu Ikeno
Keyword(s):  
Primary Silicon ◽  
Mg Alloy ◽  
Peak Hardness ◽  
Cylindrical Shape ◽  
Pressure Casting ◽  
Melt Temperature ◽  
Simple Method ◽  
Gravity Casting ◽  
Semi Solid ◽  
Silicon Particles

Both rapid and stable semi-solid slurry preparation of hypereutectic Al-14.8%Si-4.5%Cu-1.1%Mg alloy (in mass%) with fine solid granules as well as finely dispersed primary silicon particles was tried using a simple method newly developed, where the low-superheat melt passes through a gap between a rotating regular octagonal rotor and a circumscribed chill block. By examining effects of melt temperature running out from tundish, gap distance and rotational speed of rotor on solidification structure of the semi-solid slurry manufactured, the optimum making condition of the targeted semi-solid slurry was found out. Mean sizes of solid granules and primary silicon particles within the slurry, which had been made quickly with the good reproducibility, were 45μm and 20μm, respectively. Subsequently the obtained semi-solid slurries were rheocast into a cylindrical shape cavity by the use of a high pressure casting machine. It has been shown that the rheocast samples have peak hardness value between the gravity casting and the hot-extrusion, but a good age-hardenability somewhat higher than that of gravity casting.

scholarly journals Ultrasonic processing of aluminium alloys above the liquidus: the role of Zr

2020 ◽  
Vol 326 ◽  
pp. 06002
Author(s):  
Dmitry Eskin
Keyword(s):  
Solid Solution ◽  
Aluminium Alloys ◽  
Eutectic Reaction ◽  
Structure Refinement ◽  
Al Alloys ◽  
Melt Processing ◽  
Ultrasonic Processing ◽  
Solution Type ◽  
Primary Crystals

Ultrasonic melt processing (USP) is gaining quite an interest in recent years due to the benefits of this technology to the melt quality and structure refinement. A number of mechanisms have been identified that govern the effects of USP at different stages of melt processing. Technologically it is advantageous to apply USP to the fluid melt rather than to a mushy solidifying alloy. In this case heterogeneous nucleation on available or activated/multiplied substrates is the main mechanism. Among these substrates, primary crystals of Al3Zr phase were shown to be potent and effective. This paper gives a review of the own research into the role of Al3Zr in structure refinement in various groups of Al alloys, from solid-solution type to hypereutectic. This overview includes the evidence of a possible eutectic reaction between Al and Al3Zr in Al-rich alloys, mechanisms of Al3Zr formation and refinement under USP (that enables these primary crystals to be active substrates for Al and some other primary phases), the role of USP in facilitating primary solidification of Al3Zr in the Al-Zr system, and the additional benefits of solute Ti presence. The paper is illustrated with the data obtained over the last 15 years of research led by the author.

scholarly journals Stabilization Mechanism of Semi-Solid Film Simulating the Cell Wall during Fabrication of Aluminum Foam

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 333 ◽  
Author(s):  
Takashi Kuwahara ◽  
Akira Kaya ◽  
Taro Osaka ◽  
Satomi Takamatsu ◽  
Shinsuke Suzuki
Keyword(s):  
Cell Wall ◽  
Solid Fraction ◽  
Cell Walls ◽  
Aluminum Foam ◽  
Fabrication Method ◽  
Stabilization Mechanism ◽  
Solid Aluminum ◽  
Solid Film ◽  
Semi Solid ◽  
Primary Crystals

Semi-solid route is a fabrication method of aluminum foam where the melt is thickened by primary crystals. In this study, semi-solid aluminum alloy films were made to observe and evaluate the stabilization mechanism of cell walls in Semi-solid route. Each film was held at different solid fractions and holding times. In lower solid fractions, as the holding time increases, the remaining melt in the films lessens and this could be explained by Poiseuille flow. However, the decreasing tendency of the remaining melt in the films lessens as the solid fraction increases. Moreover, when the solid fraction is high, decreasing tendency was not observed. These are because at a certain moment, clogging of primary crystals occurs under the thinnest part of the film and drainage is largely suppressed. Moreover, clogging is occurring in solid fraction of 20–45% under the thinnest part of the film. Moreover, the time to occur clogging becomes earlier as the solid fraction increases.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

Dynamic studies of silicide-mediated crystallization of amorphous silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1352-1353
Author(s):  
C. Hayzelden ◽  
J. L. Batstone
Keyword(s):  
Ion Implantation ◽  
Solid Phase ◽  
Metallic Phase ◽  
Single Crystal Substrate ◽  
Free Electrons ◽  
Melt Temperature ◽  
Transmission Electron ◽  
Crystal Substrate ◽  
High Resolution Tem

Epitaxial reordering of amorphous Si(a-Si) on an underlying single-crystal substrate occurs well below the melt temperature by the process of solid phase epitaxial growth (SPEG). Growth of crystalline Si(c-Si) is known to be enhanced by the presence of small amounts of a metallic phase, presumably due to an interaction of the free electrons of the metal with the covalent Si bonds near the growing interface. Ion implantation of Ni was shown to lower the crystallization temperature of an a-Si thin film by approximately 200°C. Using in situ transmission electron microscopy (TEM), precipitates of NiSi2 formed within the a-Si film during annealing, were observed to migrate, leaving a trail of epitaxial c-Si. High resolution TEM revealed an epitaxial NiSi2/Si(l11) interface which was Type A. We discuss here the enhanced nucleation of c-Si and subsequent silicide-mediated SPEG of Ni-implanted a-Si.Thin films of a-Si, 950 Å thick, were deposited onto Si(100) wafers capped with 1000Å of a-SiO2. Ion implantation produced sharply peaked Ni concentrations of 4×l020 and 2×l021 ions cm−3, in the center of the films.

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